1. Field of Invention
The present invention relates generally to parallax devices and methods. More particularly, the present invention relates to parallax devices and methods capable of rendering autostereoscopic images in two modes.
2. Description of Related Art
Generally, three-dimensional (3D) displays may be categorized into stereoscopic displays and autostereoscopic displays (also referred to as naked-eye type 3D displays). In stereoscopic technology, users have to wear viewing aids, such as shutter glasses, so that the left and right eyes of a user may receive different images respectively, and thereby, the user may perceive a 3D image. In autostereoscopic technology, a specially designed optical element, such as a parallax barrier, is employed so as to allow the display device to provide different images to the left and right eyes of a user respectively so that the user may perceive a 3D image with naked eyes.
FIG. 1A is a schematic diagram illustrating the operation principle of conventional autostereoscopic displays. As shown in FIG. 1A, the autostereoscopic display comprises a display panel 100 and a parallax barrier 110 disposed above the display face of the display panel 100.
The display panel 100 comprises at least two substrates 102 and 104, and a liquid crystal layer 106 sandwiched therebetween. In addition, the substrate 102 has a pixel array (not shown) consisting of a plurality of pixels disposed thereon, wherein each pixel corresponds to at least one liquid crystal cell (such as, 106a, 106b) of the liquid crystal layer 106.
The parallax barrier 110 comprises: two substrates 116 and 120 opposing each other; twisted nematic cells (TN cells) 112 and 114 disposed between the substrates 116 and 120; two sets of strip electrodes 122 and 124 disposed on a surface of the substrate 116; and a surface electrode 118 substantially cover the whole surface of the substrate 120. As can be appreciated by persons with ordinary skill in the art, such autostereoscopic display may further comprises at least one polarizer (not shown for the sake of brevity); for example, a polarizer may be disposed below the display panel 100, between the display panel 100 and the parallax barrier 110, or above the parallax barrier 110. The strip electrodes 122 and 124 are arranged alternately on the substrate 116, and a strip-shaped parallax structure may be formed by respectively controlling the voltage applied on these electrodes 122 and 124. For example, when the electrode 118 and strip electrode set 122 are connected to ground voltage, whereas another strip electrode set 124 is connected to a high voltage, the TN cells 112 corresponding to the ground electrode set 122 are not driven; whereas TN cells 114 corresponding to the strip electrode set 124 (electrically connected to the high voltage) are drives. As such, when the image (light) rendered by display panel 100 passes through the parallax barrier 110, light cannot pass through the driven TN cells 114, and can merely pass through the non-driven TN cells 112; therefore, the image rendered by the display panel 100 would be transformed into an image with a parallax barrier pattern (referred to as a “parallax image” hereinbelow) that is capable of providing a left-eye image (such as the image from the pixels corresponding to liquid crystal cells 106b) and a right-eye image (such as the image from the pixels corresponding to liquid crystal cells 106a) respectively to a user's left and right eyes, and the user's brain, upon receiving the signals of the left- and right-eye images, may perceive a three-dimensional image.
Nowadays, many display devices can rotate with respect to a base or a body of an electronic device and provide images under different viewing/operating modes. For example, a display is under a landscape mode when the display is horizontally oriented (that is, the long side of the display is oriented to be horizontal); whereas a display is under a portrait mode when the display is vertically oriented (that is, the long side of the display is oriented to be vertical). However, the conventional parallax barrier as described in FIG. 1A is capable of rendering the parallax image merely in a single mode. For example, as shown in FIG. 1B, the display can only provide a three-dimensional image under the portrait mode when the strip electrode sets 152 and 154 of the parallax barrier 150 are disposed parallel to the long sides of the display device. More specifically, in this case, the image rendered by pixels 162a and 162b of the display panel 160 may pass through the TN cells (not shown) corresponding to the electrodes 152 that are connected to electrical ground, thereby providing a left-eye image (such as, an image corresponding to the image from pixels 160b) and a right-eye image (such as, an image corresponding to the image from pixels 160a) respectively to the user's left and right eyes, so that the user's brain may perceive a three-dimensional image.
Considerable problems are faced in designing displays that can render three-dimensional image under both the landscape mode and the portrait mode. For example, users have to change their viewing distances under different modes in order to perceive high-quality three-dimensional images. Briefly, the viewing distance is the distance between the user's eyes and the display screen (such as “D” illustrated in FIG. 1A). Generally, the viewing distance is in direct proportion to the eye separation as well as the distance between the parallax barrier and the pixel array. Besides, the viewing distance is in reverse proportion to the refractive index of the substrate (such as a glass substrate) as well as the pixel pitch. Accordingly, if the display is switched from the portrait mode to the landscape mode, the pixel pitches under these two modes are different which in turns result in the change of the viewing distance.
Moreover, the parallax barrier employs liquid crystal cells to form the light-shielding structure. Thus, the display, in conjunction with the liquid crystal cells of the parallax barrier, would be rotated if the user wishes to switch between the viewing modes. In this case, the liquid crystal cells in the proximity of the peripheral of the electrodes may not be rotated completely, or the distribution thereof may be uneven. As such, the user may suffer from chromatic aberration (or the color difference) due to the difference of the viewing angles.
Problems such as viewing distance or chromatic aberration may adversely affect the viewing experience of the user and the display quality of the three-dimensional image. In view of the foregoing, there exists a need in the art for providing a novel parallax barrier and method for forming three-dimensional images so as to provide users with enhanced viewing experiences.